The Effect of Sulfur on the Oxidation of Sodium-Butadiene Rubbers

Abstract

Abstract In the vulcanization of rubber and in the service performance of vulcanized rubber products, oxygen and free sulfur are always present. Consequently it is important to know the effect of sulfur on the oxidation of rubber. The present work is devoted to an investigation of the oxidation of a sodium-butadiene polymer in the presence of sulfur. Dogadkin and his associates established the fact that oxygen has an influence on the nature of the structural changes of rubber during vulcanization. The present authors have shown that any sulfur which is chemically combined with rubber does not appreciably affect the kinetics of its oxidation, and that free sulfur, in solution in rubber, interferes with autocatalytic oxidation. The higher the concentration of sulfur, the greater is this interference (see Figure 1). Introduction of sulfur into rubber during autocatalysis does not prevent the autocatalytic process, but hinders it noticeably (see Figure 2). The introduction of a secondary aromatic amine has been observed to arrest the process altogether. This behavior of sulfur can be explained by its ability to react with intermediate oxidation products, since the rate of combination of sulfur is practically constant (see Figure 3).